1. Field of the Invention
This invention relates to driving connections between two rotatable bodies having parallel but laterally-displaceable axes of rotation, the first body being hollow and the second body being located within it. The invention applies particularly to connections in which the two bodies are both shafts, the first body being a hollow shaft and the second body--which is probably solid and the driving member of the combination - being located within it.
2. Description of Related Art
The presently claimed invention thus relates especially to mechanisms of the kind described in Patent Specifications GB-B-2066361 and GB-A-2206179 which operate the valves of Internal combustion engines, which are capable of varying the valve timing during operation to suit changes in operating conditions, and in which hollow camshafts are driven by solid driving shafts located within them.
The connections between the driving shafts and camshafts, described by way of example in specification GB-B-2066361, are suitable for an engine with in-line cylinders, but with the inlet valves of the cylinders offset from the outlet valves relative to that line. The invention behind specification GB-A-2206179 arose from the need for a mechanism capable of use in a compact engine in which the cylinders are in-line, and in which the inlet and exhaust valves are also in-line with the cylinder centers. Another factor behind that invention was an increasing preference for valve-operating cams to operate directly onto bucket tappets, instead of onto rockers or levers as in GB-B-2066361.
In the design shown by way of example in specification GB-A-2206179, the driving connection between a central driving shaft and the hollow camshaft that surrounds it is made by way of an arm which projects radially from the driving shaft. The outer end of the arm has the shape of part of a cylinder whose axis lies parallel to that of the shaft. The outer end thus has a part-circular outline, and this engages rotatably in a corresponding recess formed Within a block which is mounted to slide in a radial slot formed within a flange mounted on the hollow camshaft. Such a connection has the advantage of being very compact axially, because all the essential components just recited lie in the same transverse plane relative to the axes of rotation of the driving and driven members, unlike the connections of GB-A-2066361 and also EP-A-0179581, in both of which there is an axial gap, spanned by a pin or the like, within the driving connection between the two rotatable bodies.